Control system for ovens



Oct. 31,1944. L. w. BURCH CONTROL SYSTEM FOR OVENS I Filed Sept. 25, 1940 2 0 0 3A mph/4 w a 7 3 m p w m J WE 4 y 56 MN v 0 2 T 5/ 46 \Q .W o i 4 0 In H O m J o o a m a 9 M M; a o 7 owa w H M m o aooeooooo INVENTOR ATTORNEYS Patented Oct. 31, 1944 CONTROL SYSTEM FOR OVENS Lyndon W. Burch, Pelham, N. Y., assignor to The Wllcolator Company, Newark, N. 1., a corporation of Delaware Application September 25,1940, Serial No. 358,224 8 Claims. (Cl. 177-811) iected to direct radiation is heated to a higher This invention relates to indicating systems for burners and more particularly to a novel indicating system responsive to; direct radiation from a burner, such as an oven burner, for providing a positive indication whenever the burner is ignited, or for indicating positively when the temperature controlledby the burner has reached a desired value, or both. The new system is of simple and compact construction, maybe made at low cost, and is easy to install.

For illustrative purposes, the invention will be described in connection with a gas range for indicating the condition of the oven burner, al-

' though it will be understood that the invention is not limited to this use but is applicable to furnaces and other heating appliances as well.

Gas ranges as commonly made at the present time are so well insulated and the oven burner is so completely enclosed that there is little or no evidence that the oven burner is ignited. Accordingly, it sometimes happens that the burner is left in operation unintentionally after the cooking is completed, with the result that a considerable quantity of gas is wasted. Also, in gas ranges having means for automatically lighting the oven bumer when the burner is turned on, the operator usually cannot determine whether or not the automatic lighter has actually ignited the burner, except by opening the oven door and looking through a vent hole.

One feature of the present invention, therefore, resides in the provision of a novel system temperature than the shielded element andexpands relative to the latter so as to move the free ends of the elements in one direction. However, when the oven burner is extinguished, the two elements quickly assume the same temperature, that is, the temperature in the oven, and

-their free ends move back to their initial posifor positively indicating to the operator when the oven burner is actually lighted, so as to afford an external indication equivalent to that usually provided on electric ranges by thepilot light.

A system made in accordance with my inven tion comprises a thermostat mounted in the oven adjacent the oven burner so that it receives direct radiation from the burner flame. The thermostat is not of the ordinary type which responds to temperature changes in the oven but is of a type which responds only to radiant heat from the burner, thermostats of this type being well known in the art. Preferably, the thermostat comprises two metallic elements having substantially equal coefficients of expansion, the elements being connected together at their ends but separated intermediate their ends by a medium 7 which is a poor conductor of heat, and the thertions.

Connected to the movable end 01' the radiant heat thermostat is a contact which is movable by the thermostat relative to a fixed contact. These two contacts comprise a switch. which may be included in the circuit 01' an indicating device, such as a lamp bulb, mounted outside the oven where it is visible to the operator. Preterably, the system is used with a range of the type in which the oven burner is throttled to provide a low maintaining flame when the desired temperature is reached, and the contacts are arranged so that they are normally open to deenergize the indicator when the burner is not operating. Accordingly, when the burner is ignited,-the contacts are closed by the radiant heat thermostat to energize the indicator, and the operator will therefore know that the burner is operating as called for by the position of the adjustment handle of the usual thermostatic valve. Should the burner he accidentally extinguished for any reason, the radiant heat thermostat will quickly open the contacts and deenergize the indicator, so that the operator will be warned to turn the adjustment handleto its 0112" position or relight the burner. It the bumer should fail to ignite when the adjustment handle is turned to one of its on positions, the contacts will remain open and the indicator deenergized, thereby warning the operator. The radiant heat thermostat operates independently of the oven temperature and causes the indicator to remain energized even when the oven burner is operating with a minimum maintaining flame.

Another feature of the invention resides in the provision of a novel system for indicating when the oven burner has heated the oven to the temperature for which the adjustment handle of the usual thermostatic regulating valve is set. According to the invention, a radiant heat thermostat is mounted in the oven adjacent the oven burner but is so positioned with respect to the burner that it operates only when the burner provides a substantial amount 01' radiant heat. That is, the radiant heat thermostat returns to its initial position whenever the oven burner is operating with a minimum or by-pass flame or whenever it is extinguished. The radiant heat thermostat preferably operates, a pair of contacts in circuit with an indicator, so that when the oven burner is turned on and ignited, the indicator is energized, but when the desired temperature is obtained and the thermostatic valve throttles the burner, the radiant heat therefrom is not sufiicient to hold the radiant heat thermostat in its actuated position, whereby the indicator is deenergized. If desired, the indicating system may include two radiant heat thermostats, one operating on bothminimum and normal burner flame and the other ononly normal fiame, and each thermostat may operate on indicating device so that the operator is informed whether the burner is ignited or extinguished and is also informed when the desired temperature is attained.

These and other features of the invention may be better understood by reference to the accompanying drawing, in which Fig. 1 is a schematic view showing one form of the new indicating system applied to a gas range, and

Fig. 2 is an enlarged sectional view of the thermostatic means shown in Fig. 1 for operating the indicators.

The new indicating system, as showmis applied'to a gas range including an oven Ill having a gas burner H mounted therein, the burner being provided with suitable jets Ila. Gas is supplied to the burner II from a manifold l2 through a regulator It. The regulator may be of any desired construction andcomprises the usual regulating valve (not shown) and a thermostat (not shown) responsive to temperature changes in the oven and operatively connected to the valve. In order to adjust the regulator to different temperature settings, it is provided with the usual temperature adjustment handle Ila which may be located at the front of the range. A regulator of this type is disclosed in Patent No. 2,151,541, issued to B. F. Waddell on March 21, 1939. When the handle I311 is in its "011" position, the valve in the regulator it is closed, but

when the handle is turned to one of its temperature settings, the valve is opened and allows gas to pass through a pipe line H to the burner. As soon as the oven is heated to the desired temperature, the oven thermostat shuts down the valve in the regulator i3 sothat just enough gas passes through the pipe line I4 to maintain a minimum fiame on the burner sufiicient to hold the desired temperature. It will be apparent that whenever the temperature in the oven varies, the oven thermostat actuates the regulating valve so as to supply more or less gas to the burner to counteract the temperature variation. The oven may be-provided with a safety pilot l6 of the type shown in a patent to Hahn No. 2,064,909, comprising a pilot tube I! connected to the pipe line I and supplying a relatively small amount of gas to a pilot tip it adjacent the oven burner. When the pilot is operating, the flame from the tip I8 is directed against a thermostat in the form of a U-shaped member 19 ,made of metal and having a series of holes i9a extending through the curved portion thereof near its inner edge. One arm of the thermostat i9 is mounted on the side of the oven, as shown at 20, so that the pilot flame impinges on the inner edge of thecurved portion adjacent. the holes Ma. The free arm' 2! of the thermostat l9 engages a rod 22 slidably mounted in the mounted on the range.-

oven and extending through the oven wall, the outer end of the rod engaging a spring-pressed lever mechanism 23 which operates a safety valve 21 located-in the pipe line Hf between the pilot tube I! and the oven burner.

When the pilot is ignited, the flame from the tip it heats the adjacent inner edge of the curved portion of thermostat I! to a higher temperature than the remote outer edge, due to the fact that the holes lid prevent rapid conduction of heat to the outer edge, and, as a result, the inner edge expands relative to the outer edge and causes the free arm 2! to move away from the fixed arm and open the safety valve 24 through rod 22 and lever mechanism 23 against the spring action-0f the latter. If the pilot flame should accidentally be extinguished, the inner edge of the curved portion of thermostat I! will cool to the temperature of the outer edge and cause the free arm 2| to move back toward the fixed arm, whereby the valve 24 closes under the action of the spring-pressed lever mechanism 22 and shuts oil the supply of gas.

The pilot, if desired, may have an automatic ignition system comprising a fixed contact 28 mountedadjacent the free arm of thermostat is on the side opposite the rod 22. The fixed contact 26 is insulated from the range and is connected to one terminal of an electric igniter 21 mounted adjacent the pilot tip it and adapted when energized to light the pilot when gas is supplied through the tip. Connected to the other terminal of the igniter 21 is a wire 28 which leads to a resistance 28a connected to one side of the secondary winding of a transformer 29 The primary winding of the transformer may be connected to the domestic lighting circuit 20. At its opposite side, the secondary winding of the transformer is connected to a switch 2|, grounded to, the

- frame of the range, as shown at 32, the thermostat is also being grounded to the range, as shown at 33. The switch 3| may be operated by a suitable cam 34 on the shaft of the adjustment handle in, so that when the latter is in its 01f position the switch 3! is open, but when the handle is moved to any one of its temperature settings, the cam closes the switch. Accordingly, when the handle its is turned from its "ofl position and the thermostat is is in the normal position shown in Fig. 1, a circuit is established through the igniter 21 from the ground 33, thermostat I9, contact 26, igniter 21, wire 28, the secondary winding of the transformer, and switch 3| to the ground connection 32, whereupon the igniter lights the pilot. when the pilot flame strikes the thermostat is, the arm 2| moves away from the fixed arm so as to open the safety valve 24, andat the same time it disengages the fixed contact 26 so as to break the circuit through the igniter.

Mounted in the oven l0 adjacent the main burner H are two thermostats 26 and 31 which are responsive only to direct radiation from the main burner. The thermostats 36 and 31 may take any desired form but preferably comprise tubular members 32 and 381:, respectively, made of metal and each having a pair of diametrically opposed slots 39 and 39a, respectively, extending lengthwise of the tube but terminating short of the ends of the tube, the slots being so disposed that they divide each tube into two opposed ele-' ments one of which faces the burner and the.

At'their inner ends. the tubular members are mounted in a hollow metal casing 48 so that the tubes communicate with the interiorof the casing. Fitted closely in the free ends of the tubes are metal collars 4| and 4la. respectively, supporting rods 42 and 42a, respectively, which extend inwardly through the tubes in spaced relation thereto and project into the casing 48. The free ends of the rods 42 and 42a coact with fixed contacts 43 and 43a, respectively, mounted on suitable insulating supports 44, the fixed contacts and their corresponding rods forming separate control means for a purpose to be described presently.

The side of the casing 48 opposite the tubular members 88 is provided with a hollow boss 48 having a generally spherical portion 41 intermediate its ends. A metal bracket 48 has a circular opening therein for receiving one end of the spherical portion 41 and is connected by bolts 48 to a plate- 58 having a similar opening for receiving the other end of the spherical portion. Thus, the spherical portion 41 and the coacting bracket 48 and plate 58 provide a universal mounting for the housing so that the latter may be adjusted to position the tubular members 88 relative to the oven burner. The bracket 48 is preferably connected to the adjacent side wall of the oven so that it is grounded, as shown at 5!. Threaded on the outer end of the hollow boss 46 is a compression fitting 53 engaging an enlargement 54 on the end of a metal tube 55 which extends through the adjacent wall of the oven. The fitting 53 is screwed tightly on the boss so as to clamp the enlargement 54 against the outer end of the boss.

The fixed contact 43 has a wire 51 connected thereto which leads from the interior of the casing through the boss 46 and tube 55 to the outside of the oven where it is connected to one terminal of a suitable indicating device, such as an incandescent lamp 58 adjacent the handle 53a. The other terminal of the lamp is connected by a wire 58 to the resistance 28a and the transformer. Similarly, the fixed contact 43a has a wire 60 connected thereto leading through the boss 46 and tube 55 to one terminal of a second lamp 6| ad acent the handle l3a, the

other terminal of the lamp being connected by a wire 82 to the resistance 28a.

In operation, when the burner is extinguished and the adjustment handle l3a is in its "off position, the rods 42 and 42a disengage their corresponding contacts so that the lamps 58 and 8| are deenergized. When the operator turns the handle I341 to one of the temperature settings, the switch 3| is clos d and connects the igniter 21 in circuit with the secondary winding of the transformer so that the pilot is lit, and as soon as the safety valve 24 opens, the pilot ignites the main burner H which is now supplied ith gas through the regulator l3. Radiant heat from the flame of the main burner strikes the adjacent thermostat 36 and heats the adjacent side of this thermostat to a higher temperature than the remote side, with the result that the adjacent side expands relative to the remote side and causes the free end of the thermostat to move away from the burner and tilt the rod 42 ina counter-clockw se direction, thereby engaeing the inner end of the rod with its fixed contact 43. A circuit is then established through the lamp 58 from the ground connection 5| through bracket 48, housing 40, tube 38,

3 cousiu, rod", contact 4:. wire 51, lamp 88,

,wire 58. the secondary winding of the transformer 28, and switch 8| to the ground connection 32. Thelamp 88 is thus energized and informs the operator that the main burner is is- Similarly, thermostat 31 is subjected on one side to direct radiation from the main burner, although the radiant heat on this thermostat is not as intense as it is on the thermostat 38 due to the fact that the thermostat 31 is located at a greater distance from the main burner and is partly shielded by the thermostat 36. However,

when the main burner is operating with a normal flame, as when it is heating the oven to the temperature for which handle l8a is set, the radiant heat on the adjacent side of thermostat 81 is sumcient to cause this side to expand relative to the opposite side, so that the free end of the thermostat 31 moves away from the burner and engages its rod 42a with the corresponding fixed contact 48a. A circuit is thus established from the ground connection 5| through bracket 48, casing 48, tube 38a, rod 421:, fixed contact 4311, wire 68, lamp 8|, wire 62, the secondary winding of transformer 28, and switch 8| to the ground connection 32. When the temperature in the oven has reached that for which the handle We is set, the thermostatic regulator l3 cuts down the supply of gas to the burner H so that the latter is throttled to a minimum or maintaining flame. The radiant heat from this minimum or temperature-maintaining flame is suflicient to maintain the required temperature differential between the opposed sides of the thermostat 38 to cause the latter to hold its rod 42 in engagement with contact 43, so that the lamp 58 remains energized. However, radiant heat from the minimum or temperature-maintaining flame is not suiiicient to maintain the required temperature differential in the thermostat 31, and the opposed sides of the latter tend to approach a uniform temperature so that the tube 38a returns toward its normal position and disengages its rod 42a from the fixed contact 43a. As a result, the circuit through lamp 6| is broken and the latter deenergized, thereby indicating to the operator that the desired temperature has been reached.

If for any reason the oven burner II should be extinguished, the opposed sides of the thermostat 38 will quickly assume a uniform temperature and cause the free end of the thermostat to move toward the burner and disengage the rod 42 from its fixed contact 43. The circuit through the other lamp 58 is then broken and the latter deenergized to indicate to the operator that the main burner is not operating.

The new indicating system is of simple construction and is readily installed on the range. The operator may determine by a glance at the indicators 58 and ti whether the oven burner is actually operating as called for by the position of the control handle l3a. and whether the oven has been heated to the temperature for which the handle is set. In the event that the burner fails to operate when the regulator and safety valves are open, the'operator is immediately and positively informed of the dangerous condition by the absence of illumination from the lamp 58. If the current for energizing the indicating system should be interrupted, the lamps 58 and BI will merely fail to light when the operator turns on the oven regulator, and by their failure to light the operator is warned that either the burn er has not ignited or the indicating system has sal mounting lor'thecasing til. the latter may be readily adjusted to place the tubes II and Ila in their proper positions relative to the adjacent burner jets i la, and when the adjustment is completed the bolts 4! may be tightened to hold the I parts securely in position.

With the new system, it is unlikely that the operator will accidentally leave the burner turned on after the food-is removed from the oven, because the indicator lamp It remains illuminated as long as the burneris operating, even with a minimum flame. It will be observed that the system of my invention as illustrated provides the same kind of indication that the oven heater is turned on and that the oven has reached the desired temperature, which is usually provided on electric ranges by incandescent lamps. While in the illustrated form of my invention the indicators are energized only when their thermostats are actuated by the radiant heat, it will be understood that the parts may be arranged to energize the indicators whenever the radiant heat thermostats return to their normal positions and to deenergize the indicators when their thermoable normally with a flame variable in accordance with changes in the oven temperature, an indicating system comprising a thermostat mounted adjacent the burner and responsive only to direct radiation therefrom and responsive to any flame thereon within the normal range of operat on of the burner, said thermostat being operable substantially independently of the oven temperature, a movable contact operated by the thermostat, a flxed contact coacting with the movable contact, means for grounding one of the contacts to the range, a current source on the range having one terminal grounded to the range and the other terminal connected to the other contact, and an indicating device in circuit with said contacts and current source, the indicating device beingoperabie under control 01 thethermostat to indicate positively when the oven burner is ignited.

2. In combination with a range having an r-ven. a ma n burner therein operable normally with a flame variable in accordance with changes in the oven temperature, and a temperature adj stment handle outside. the oven for selecting dlflerent oven temperatures, an ind cating system comprising a thermostat mounted adjacent the oven burner and responsive only to direct radiation therefrom and responsive to any flame thereon within the normal range of operation of the burner. the thermostat being operable substantially independently of the oven temperature. a

indicating device being operable under control or the thermostat through the switch to-provide a positive indication when the burneris ignited, and a second switch in circuit with the current source and the indicating device and operable by said temperature adjustment handle. 7

8. In combination with a gas, oven, or the like. having a main burner in the oven operable normall! with a flame variable in accordance with changes in the oven temperature, an indicating system comprising a thermostat operable substantially independently of the oven temperature and responsive only to direct radiation and responsive to any flame on the burner within the normal range of operation oi the burner, a casing in the oven for mounting the thermostat adjacent the burner in position to receive direct radiation therefrom and adjustable relative to the burner to vary the position of the thermostat, a switch in the casing operatively connected to the thermostat. an indicating device outside the oven, wiring extending from the indicating device through the oven wall to the interior of the casing aand connected to the switch, and a current source in circuit with the switch and indicat ng device, the thermostat being operable through the switch and indicating device to provide a positive indication when the burner is ignited.

4. In combination with a gas oven, or the like, having a main burner therein operable normally with a flame variable in accordance with changes in the oven temperature, an indicat ng system comprising a thermostat mounted adjacent the burner and responsive only to the presence of a flame thereon and responsive only to a flame therlbn corresponding to at least the normal minimum rate of operation or the burner, the thermostat being operable substantially independently oi the oven temperature, control means operated by the thermostat, and an indicating device under control of said means, the thermostat being operable'through the control means and indicating device to provide a positive indication when the burner is operating normally.

5. In combination with a gas oven. or the like, having a main burner therein operable normally with a flame variable in accordance w th changes in the oven temperature, an indicating system comprising a thermostat mounted adjacent the burner and responsive only to the presence of a flame thereon and responsive to any flame within the normal range of operation of the burner, the thermostat being operable substantially independently of the oven temperature, adjustable means for mounting the thermostat adjacent the burner I in position to receive direct radiation therefrom, control means operated by the thermostat and disposed in the adjustable means. and an indicating device under control 01' the control means, the thermostat being operable through the control means and indicating device to provide a posit ve indication when the burner is operating within its normal range.

6. In combination with a'gas range having an oven, a main burner therein, and adjustable means responsive to changes in the oven temperature for throttling the supply of gas to the burner when the oven reaches the temperature for which said means is adjusted. said adjustable means being adapted to provide a minimum flame on said burner sufllcient to maintain said lastmentioned temperature, an indicating system comprising a thermostat mounted near the oven burner and responsive only to a flame on the burner above a minimum temperature-maintenance flame, control means operated by said thermostat, and an indicating device under control of said control means, the thermostat being operable through the control means and indicating device to provide a positive indication when the oven reaches the temperature for which said adjustable means is adjusted and said burner is on a minimum temperature-maintenance flame or is extinguished.

7. In combination with a gas range having an oven, a main burner therein, and adjustable means responsive to changes in the oven temperature for throttling the supply of gas to the burner when the oven reaches the temperature for which said means is set, said adjustable means being adapted to provide a minimum flame on said burner suflicient to maintain said last-mentioned temperature, an indicating system comprising a thermostat mounted near the oven burner and responsive only to a flame on the burner above a minimum temperature-maintenance flame, a second thermostat mounted near the oven .bumer and responsive to any flame thereon within the normal range of operation of the burner, and an indicating device under control of each of said thermostats, the indicating devices together providing under control of the thermostats positive indications when the burner is ignited and when it is operating on minimum temperature-maintenance flame.

8. In combination with a gas range having an thereon within the normal range of operation of the burner, a casing in the oven for supporting the thermostats and grounded to the range, a movable contact in the casing for each of said thermostats and operable thereby, said contacts being electrically connected to the casing, a fixed contact in the casing coactin'g with each movable contact and insulated from the casing, indicating devices connected to the fixed contacts, and a current source connected in circuit with the indicating devices and having one terminal grounded to the range, the indicating devices together providing under control of the thermostats positive indications when the burner is ignited and when it is operating on minimum temperature-maintenance flame.

'LYNDON W. BURCH. 

